Stabilized xylidine and process for preparing same



Patented Jan. 20, I948 STABILIZED XYLIDINE AND PROCESS FOR PREPARING SAME Anthony E. Robertson, Roselle, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application October 30, 1943, Serial No. 508,396

2 Claims.

This invention relates to the stabilization of alkaryl amines against deterioration by discoloration, etc., during storage.

The alkaryl-amines such as toluidine, xylidine, etc., are normally substantially colorless when freshly prepared or freshly distilled, but tend to darken in color during storage, the undesirable results being greatly accelerated by storage at elevated temperatures.

The object of the present invention is to stabilize such alkaryl amines against discoloration during storage.

Broadly, the invention comprises adding to the alkaryl amines a small amount of a stabilizer comprising essentially carbon disulfide.

Instead of using carbon disulfide, other equivalent materials may be used such as derivatives of carbon disulfide such as the reaction products of alcohols and carbon disulficle, e. g., isopropyl xanthic acid and its sodium salt.

Although the amount of the stabilizer to be used may vary according to the intended duration of storage and the temperature of storage, as well as according to the particular alkaryl amine and the particular stabilizer used, in gen eral about .01% to 1.0% of stabilizer will be sufficient, and usually about .05% to 0.5% by weight of stabilizer will be found most practical for giving satisfactory results.

Although the invention is intended to apply broadly to the stabilization of any type of alkaryl amines, it is believed particularly applicable to alkaryl amines having from 1 to 3 alkyl carbon atoms. The invention has been found very successful for the stabilization of xylidine, either the pure separate isomers, or mixtures thereof.

Other alkaryl amines which may be stabilized include the toluidines, ortho, meta or para, or mixtures thereof, the several ethyl aniiines, cumidine (which in isopropyl-aniline), etc. Dialkylated and trialkylated aryl amines are preferred. Although the invention is particularly applicable to such alkaryl, amines, it may also be used for stabilizing naphthylamines, and the various derivatives of aniline in which either or both of the hydrogens of the amino group are substituted by hydrocarbons, i. e., either alkyl or aryl groups, e. g., in N-monomethyl aniline, N-dimethyl aniline, N-monoethyl aniline, etc. Thus although the invention is particularly applicable to alkaryl primary amines, other amines such as secondary and tertiary amines may also be used.

The various above described aromatic amines may be used alone or together with a diluent, such as a hydrocarbon solvent, e. g., naphtha.

2 Such diluents may be present in amounts ranging from only a few per cent up to 10, 20 or even times the volume of the aromatic amines.

In carrying out the invention, it is preferred to add the stabilizer to the alkaryl amines as soon as the latter has been prepared, or immediately after distillation.

The following experimental data will illustrate the advantages of the invention:

A sample of freshly redistilled xylidine (a mixture of various isomeric Xylidines) was tested for color stability by heating in an open bottle for six hours at 194 F. as an accelerated stability test. At the end of this time the optical density, which is an indication of discoloration or darkening of color, had increased from .04. to 2.3. On the other hand, 0.1% of carbon disulfide was added to another sample of the same redistilled xylidines and the mixture was subjected to the same accelerated stability test. The mixture, which had an optical density of .02 at the beginning of the test, was found to still have an optical density of .02 at the end of the heating, thereby indicating that the 0.1% of carbon disulfide added completely stabilized the xylidine against discoloration during the severe accelerated stability test of heating for six hours at 194 F.'in an open bottle.

Although the mechanism of the operation of the invention is not understood with certainty, it is believed that during the storage, the aromatic amine must necessarily undergo some chemical reaction such as oxidation and/or polymerization. which is subject to inhibition by the carbon disulfide.

It is not intended that this invention be limited to the particular materials which have been given merely for the sake of illustration, nor by any theory as to the mechanism of the operation of the invention, but only by the appended claims in which it is intended to claim all novelty inherent in the invention as well as all modifications coming within the scope andspirit of the invention.

I claim:

1. A product comprising xylidine and a sumcient amount of carbon disulfide to stabilize said xylidine against discoloration during storage.

2. The method of stabilizing xy idine against discoloration during storage which comprises adding thereto about .05%-0.5% of carbon disulfide.

ANTHONY E. ROBERTSON.

(References on following page) 3 Number Name Date REFERENCES 0mm 1,741,206 Btackhouse 1320.31, 1929 r 1,947,578 Bond Feb. 20, 1934 'fi gfggig ggg gff m o m the 1,882,758 ammn Oct. 18, 1932 UNITED STATES PATENTS 5 REFERENCES Number Name Dat Chem. Abstracts, v01. 28 (1934), p. 5418.

9 1,358,324 Moore NOV. 9, 1 2 Chem. Abstx acts, vol. 28 (1934), p. 1335. 

